Of bats there are one or two genera (Barbastellus, Plecotus) which seem to be mainly or wholly Palæarctic, but the classification of these animals is in such an unsettled state that the distribution of the genera is of little importance.
In the next order, Insectivora, we have almost the entire family of the Moles confined to the region. Talpa just enters Northern India; and Urotrichus is common to Japan and North-Western America, but the remaining genera, six in number, are all exclusively Palæarctic.
Among Carnivora we have Nyctereutes, the curious racoon-dog of Japan and North-Eastern Asia; Lutronectes, an otter peculiar to Japan; and the badger (Meles), which ranges over the whole region, and just enters the Oriental region as far as Hongkong; Æluropus, a curious form of the Himalayan panda, inhabiting the high mountains of Eastern Thibet; and Pelagius, a genus of seals, ranging from the shores of Madeira to the Black Sea.
The Ungulata, or hoofed animals, are still more productive of forms peculiar to this region. First we have the Camels, whose native home is the desert region of Central and Western Asia and Northern Africa, and which, even in their domesticated condition, are confined almost wholly within the limits of the Palæarctic region. Of Deer we have six peculiar genera, Dama and Capreolus found in Europe, with Elaphodus, Lophotragus, Hydropotes, and Moschus, confined to Northern China and Mongolia. The great family Bovidæ—comprising the oxen, sheep, goats and antelopes—furnishes no less than seven peculiar Palæarctic genera. These are Poephagus, the yak of Thibet; Addax, a well-known antelope of Northern Africa and Syria; Procapra, Pantholops and Budorcas, antelopine genera peculiar to Thibet and Mongolia; with Rupicapra (the chamois), and the extraordinary large-nosed antelope Saiga, confined to Europe and Western Asia. Besides these we have Capra (the wild sheep and goats), all the numerous species of which, except two, are exclusively Palæarctic.
Coming to the Rodents, we have again many peculiar forms. Of Muridæ (the mouse and rat tribe), we have six peculiar genera, the more important being Cricetus, Rhombomys Sminthus, and Myospalax. Of Spalacidæ (mole-rats) both the Palæarctic genera, Ellobius and Spalax, are peculiar. Ctenodactylus, a genus of the South American family Octodontidæ, is found only in North Africa. To these we may add Myoxus (the dormice) and Lagomys (the pikas or tail-less hares) as essentially Palæarctic, since but one species of each genus is found beyond the limits of the region.
Birds.—It appears to have been the opinion of many naturalists that the Palæarctic region could not be well characterised by its peculiar genera of birds. In Mr. Sclater's celebrated paper already referred to, he remarks, "It cannot be denied that the ornithology of the Palæarctic region is more easily characterised by what it has not than by what it has," and this has been quite recently quoted by Mr. Allen, in his essay on the distribution of North American birds, as if it represented our present knowledge of the subject. But, thanks to the labours of Dr. Jerdon, Mr. Swinhoe, Père David and others, we have now learnt that a large number of birds included in the Indian list, are either mere winter emigrants from Central Asia, or only inhabit the higher ranges of the Himalayas, and thus really belong to the Palæarctic region. The result is, that a host of genera are now seen to be either exclusively or characteristically Palæarctic, and we have no further difficulty in giving positive ornithological characters to the region. In the tables appended to this chapter, all these truly Palæarctic genera will be found printed in italics, with an indication of their distribution, which will sometimes be found more fully given under the respective families in the fourth part of this work. Referring to this table for details we shall here summarise the results.
Of the Sylviidæ or warblers, no less than fourteen genera are either exclusively or characteristically Palæarctic, of which Locustella, Sylvia, Curruca and Erithacus are good examples. Of the oriental family Timaliidæ, the genus Pterorhinus is Palæarctic. Of Panuridæ, or reedlings, there are four peculiar genera (comprising almost the whole family); of Certhiidæ, or creepers, one—Tichodroma—which extends southward to the Abyssinian highlands. Of Paridæ, or tits, one—Acredula; of Corvidæ, or crows, four—Pica (containing our magpie) being a good example; of Fringillidæ, or finches and buntings, twelve, among which Acanthis, Pyrrhula and Emberiza are good illustrations; of Alaudidæ, or larks, there are two peculiar genera. Leaving the Passeres we next come to peculiar forms among the gallinaceous birds: Syrrhaptes among the Pteroclidæ or sand grouse; four genera of Tetraonidæ or grouse and partridges, and five of Phasianidæ or pheasants, comprising some of the most magnificent birds in the world. Lastly among the far-wandering aquatic birds we have no less than five genera which are more especially Palæarctic,—Ortygometra, the corn-crake, and Otis, the great bustard, being typical examples. We may add to these, several genera almost confined to this region, such as Garrulus (jays), Fringilla (true finches), Yunx (wrynecks) and some others; so that in proportion to its total generic forms a very large number are found to be peculiar or characteristic.
This view, of the high degree of speciality of the Palæarctic region, will no doubt be objected to by some naturalists, on the ground that many of the genera reckoned as exclusively Palæarctic are not so, but extend more or less into other regions. It is well, therefore, to consider what principles should guide us in a matter of this kind, especially as we shall have to apply the same rules to each of the other regions. We may remark first, that the limits of the regions themselves are, when not formed by the ocean, somewhat arbitrary, depending on the average distribution of a number of characteristic forms; and that slight local peculiarities of soil, elevation, or climate, may cause the species of one region to penetrate more or less deeply into another. The land boundary between two regions will be, not a defined line but a neutral territory of greater or less width, within which the forms of both regions will intermingle; and this neutral territory itself will merge imperceptibly into both regions. So long therefore as a species or genus does not permanently reside considerably beyond the possible limits of this neutral territory, we should not claim it as an inhabitant of the adjacent region. A consideration of perhaps more importance arises, from the varying extent of the range of a genus, over the area occupied by the region. Some genera are represented by single species existing only in a very limited area; others by numerous species which occupy, entirely or very nearly, the whole extent of the region; and there is every intermediate grade between these extremes. Now, the small localised genera, are always reckoned as among the best examples of types peculiar to a region; while the more wide-spread groups are often denied that character if they extend a little beyond the supposed regional limits, or send one or two, out of a large number of species, into adjacent regions; yet there is some reason to believe that the latter are really more important as characterising a zoological region than the former. In the case of a single isolated species or genus we have a dying-out group; and we have so many cases of discontinuous species of such groups (of which Urotrichus in Japan and British Columbia, Eupetes in Sumatra and New Guinea are examples), that it is quite as probable as not, that any such isolated species has only become peculiar to the region by the recent extinction of an allied form or forms in some other region. On the other hand, a genus consisting of numerous species ranging over an entire region or the greater part of one, is a dominant group, which has most likely been for some time extending its range, and whose origin dates back to a remote period. The slight extension of such a group beyond the limits of the region to which it mainly belongs, is probably a recent phenomenon, and in that case cannot be held in any degree to detract from its value as one of the peculiar forms of that region.
The most numerous examples of this class, are those birds of the temperate regions which in winter migrate, either wholly or partially, into adjacent warmer countries. This migration most likely began subsequent to the Miocene period, during that gradual refrigeration of the temperate zones which culminated in the glacial epoch, and which still continues in a mitigated form. Most of the genera, and many even of the species of birds which migrate southwards in winter, have therefore, most likely, always been inhabitants of our present Palæarctic and Nearctic regions; permanent residents during warm epochs, but only able now to maintain their existence by migration in winter. Such groups belong truly to the temperate zones, and the test of this is the fact of their not having any, or very few, representatives, which are permanent residents in the adjacent tropical regions. When there are such representative species, we do not claim them as peculiar to the Northern regions. Bearing in mind these various considerations, it will be found that we have been very moderate in our estimate of the number of genera that may fairly be considered as exclusively or characteristically Palæarctic.
Reptiles and Amphibia.—The Palæarctic region possesses, in proportion to its limited reptilian fauna, a full proportion of peculiar types. We have for instance two genera of snakes, Rhinechis and Halys; seven of lizards, Trigonophis, Psammodromus, Hyalosaurus, Scincus, Ophiomorus, Megalochilus, and Phrynocephalus; eight of tailed batrachians, Proteus, Salamandra, Seiranota, Chioglossa, Hynobius, Onychodactylus, Geotriton, and Sieboldia; and eight of tail-less batrachians, Bombinator, Pelobates, Didocus, Alytes, Pelodytes, Discoglossus, Laprissa, and Latonia. The distribution of these and other Palæarctic genera will be found in our second vol. chap. xix.